Efficient Plant February 2020 - 19

motors

Bolster
Step-Motor
Reliability
RELIABLE OPERATION of step-motor systems
begins with the sizing and selection process. Avoid
specifying a motor that is too large. You'll generally
end up spending more money than is necessary
and/or generating too much heat for an application.
If the motor is too small, it may not provide the
right amount of torque for reliable motion control.
These tips can help you specify a step-motor system
that ensures reliable operation for the life of your
machine or process.

These tips will help you improve step-motor performance and reliability.

NEVER USE THE HOLDING-TORQUE
SPECIFICATION TO SIZE A STEP MOTOR.
The holding-torque specification defines the amount of torque the
motor provides when at rest. Because output torque falls as speed
increases, holding torque is a poor indication of the torque the motor
produces when rotating.

ESTIMATE A TORQUE MARGIN WHEN REVIEWING
SPEED-TORQUE CURVES.
While torque produced at a specific speed by a step motor is shown
in published curves, information represents best-case performance.
Pad your torque requirements by 50% to 100% for better results and
safeguard against stalls that can stop production.

ADHERE TO THE SUPPLIER'S DRIVE AND POWERSUPPLY RECOMMENDATIONS.
The specific drive and power-supply voltage used in creating speedtorque curves is critical to achieving published performance. Whenever possible, use the same drive and power-supply voltages in the
machine. The rated supply voltage corresponds to speed, torque, and
power. Using a supply voltage other than the published one can result
in the motor not achieving expected torque.

KEEP THE MOTOR CASE TEMPERATURE UNDER
212 F (100 C).
Use the idle-current-reduction feature of the stepper drive to automatically reduce the motor current when the motor is in holding position.
While step motors are designed to run hot, surface temperatures that
exceed 212 F can lead to motor failure.

IF THE STEP MOTOR VIBRATES EXCESSIVELY
ONCE INSTALLED IN THE MACHINE, IT COULD BE
DUE TO NATURALLY OCCURRING RESONANCE.
A simple solution to this problem is running the motor a little faster
or slower, if possible. Another solution is reducing the current setting
on the drive, but not to the point that the motor stalls. A stepper drive
with microstepping or anti-resonance also serves as a solution as it
will reduce or eliminate the motor's natural resonance.

Following these tips when sizing, selecting, and operating step motors
will increase the success of your application and the long-term reliability
of your machine or process. If in doubt about the information presented, contact your step-motor supplier. EP
-Eric Rice, Applied Motion Products

For more information, contact Applied Motion Products, Watsonville, CA, at applied-motion.com
FEBRUARY 2020

EP2002rmcappliedmotion.indd 19

EFFICIENTPLANTMAG.COM |

1/29/20 11:21 AM

http://www.applied-motion.com http://www.EFFICIENTPLANTMAG.COM

Efficient Plant February 2020

Table of Contents for the Digital Edition of Efficient Plant February 2020